[Zope] ZPT and CSS

Hi Zopers Trying to improve my ZPT pages I wanted to make use of Cascading Style Sheets (CSS). While the styles in my CSS file are properly rendered when I open the HTML file directly in the browser (Mozilla 1.4.1) they completely disappear when I view the same page through Zope!!! What is Zope doing? May it be that the CSS cannot be located because of the base url inserted by Zope? best wishes Andre